Fun With Hydrophobic Sand.

by David Klemke on November 15, 2012

There’s been something of an explosion of hydrophobic (something that’s literally water proof) products recently. Many of the products are pretty novel ideas that have practical applications like shoes and boots but there are many other, stranger devices like this device that can pick up condiments spilled on a table. I thought I had seen most of the cool applications of hydrophobic coatings already until I came across this little gem the other day and the science behind what you see in it is quite awesome.

So this sand, called Magic Sand which you can buy or even make yourself, starts to act in a rather odd way once it gets under water. You’ll notice that it sometimes takes a bit of effort to actually get it under the water and that’s because, just like oil, it would prefer to float on top of it rather than mix with it. Once its under there however it seems to stop acting like a power and starts acting like a semi-solid, being quite malleable. Once you take it out of the water however it returns to its former powder state, losing any of the properties it just had.

The reason for this is pretty simple and would have some pretty cool effects if they had a deeper tank or a pressurized container. Once the power is under water its put under pressure by all the water molecules around it, much like SCUBA divers are. This forces it to clump together which is what gives the sand its apparently malleability. Once its removed from the water this pressure is gone and we’re left with the powder we had before hand. If you had a really deep tank and did the same experiment the sand would become less and less malleable as the depth increased as the pressure exerted on it would continue to go up. Dropping some of this into the Mariana Trench would likely give you a hydrophobic rock by the time it reached the bottom, and an incredibly dense one at that.

The sand also has a practical purpose other than being a cool science based toy. Originally it was developed as a solution for surface oil spills where you’d cover the spill with the dust which would then be heavy enough to sink allowing for recovery. That method is unfortunately too expensive to be used and most clean ups instead rely on booms and specially designed ships but it is being tested for other applications.

Man if my younger self could see me now. He’d be wondering why the hell a grown man was so interested in all these boring, educational things. I seriously can’t get enough of them now 😀